One of our most popular portfolios, second only to Buffett's, is that of George Soros' Soros Fund Management. Soros ranks No. 22 in Forbes' list of the world's billionaires, with a net worth of $20 billion.

In the fourth quarter, according to the most recent 13F filing with the Securities and Exchange Commission, Soros sold out of over 300 positions in the fourth quarter, including Amazon (AMZN), Biogen Idec (BIIB) and AT&T (T).

But what did the billionaire buy? Here's a look at seven stocks that Soros bought in the most recently reported quarter, which are all part of the top 30 holdings tracked on Stockpickr.

7. Steel Dynamics

In the fourth quarter, Soros initiated a new 1 million-share position Steel Dynamics (STLD), which comprises 0.31% of the total portfolio.

Stock Overview: Steel Dynamics, together with its subsidiaries, is a domestic manufacturer of steel products and metals recycler. It has a market cap of $3.1 billion. The stock, which yields 2.8% and has a short interest ratio of 1.8, closed up 25 cents, or 1.9%, at $14.35 on Friday.

Analyst Ratings: Of 14 analysts covering the stock, six rate it a buy, and eight rate it a hold. TheStreet Ratings has a C+ hold rating on Steel Dynamics, with a $17.31 price target.

6. Freeport-McMoRan

Freeport-McMoRan (FCX) was another new position for Soros Fund Management in the fourth quarter, with 370,300 shares purchased, for 0.33% of the total portfolio.

Stock Overview: Freeport is an international mining company. It engages in the mining of copper, gold and molybdenum. It has a market cap of $37.5 billion. The stock, which yields 2.5 and has a short interest ratio of 1.1, closed off 72 cents, or 1.8%, at $38.78 on Friday.

In the fourth quarter, Soros increased his position in Delta Air Lines (DAL) by 1.74 million shares, or over 6,000%, to 1.77 million shares. The stock comprised 0.34% of the total portfolio as of the end of the quarter.

Stock Overview: Delta operates as an airline, providing scheduled air transportation for passengers and cargo throughout the United States and around the world. It has a market cap of $8 billion. The stock, which has a short interest ratio of 0.7, closed down 10 cents, or 1.1%, at $9.37 on Friday.

Analyst Ratings: Of 12 analysts covering the stock, 11 rate it a buy, and one rates it a hold. TheStreet Ratings has a C hold rating on Delta.

Stock Overview: KeyCorp is a financial holding company that, through its subsidiaries, provides retail and commercial banking, commercial leasing, investment management, consumer finance and investment banking products and services to its clients. It has a market cap of $7.6 billion. The stock, which yields 1.5% and has a short interest ratio of 0.5, closed up 8 cents, or 1%, at $8.02 on Friday.

Analyst Ratings: Of 24 analysts covering the stock, seven rate it a buy, 13 rate it a hold, and four rate it a sell. TheStreet Ratings has a C+ hold rating on KeyCorp.

Stock Overview: Wells Fargo provides financial services through subsidiaries engaged in various businesses, including wholesale banking, mortgage banking, consumer finance, equipment leasing and agricultural finance. It has a market cap of $165.6 billion. The stock, which yields 1.5 and has a short interest ratio of 1.1, closed up 26 cents, or 0.8%, at $31.66 on Friday.

Analyst Ratings: Of 23 analysts covering the stock, 19 rate it a buy, three rate it a hold, and one rates it a sell. TheStreet Ratings has a C+ hold rating on Wells Fargo, with a $36.43 price target.

Stock Overview: Comverse designs, manufactures, markets and supports computer and telecommunications systems and software for multimedia communications and information processing applications. It has a market cap of $1.3 billion. The stock, which has a short interest ratio of 1.1, closed up 6 cents, or 1%, at $6.22 on Friday.

Analyst Ratings: Of eight analysts covering the stock, five rate it a buy, and three rate it a sell. TheStreet Ratings has a D- sell rating on Comverse.

In the fourth quarter, Soros essentially bought a new position in Google (GOOG), increasing his previous stake by 258,770 shares to 259,790 shares. The stock is his fourth-largest holding as of the end of the quarter, representing 4% of the total portfolio.